1. Field of the Invention
The present invention relates to an electrostatic precipitator, in particular an electrostatic precipitator that is capable of collecting fine particles that have been charged by corona discharge by rotating adsorption plates.
2. Description of Related Arts
Traditionally, so-called “industrial waste gases”, such as exhaust from boilers at industrial installations and a large quantity of soot discharged from power stations, before their release into the atmosphere, have been on occasion subjected to an air cleaning process to remove fine particles that may pollute the atmosphere (such as mist and dust containing various powdery or oily substances and moisture from industrial waste gases). The release of industrial waste gases containing these particles directly into the atmosphere poses a serious threat to the earth environment; and recovery of these noxious substances is required by law in some countries and local governments. In urban areas, air pollution from automobile exhaust and others creates a serious condition. Some homes are equipped with and use indoor air purifiers. In many of the kitchens of restaurants, smoke generated during cooking and otherwise contaminated air are cleansed by air purifiers before being released outside.
For the dust collecting devices to recover the fine particles contained in contaminated air, the cause for air pollution and how to purify air, many types based on various principles are known. Specifically, classified based on theories of particle collection, filtration, gravity, inertia, centrifugation, electricity, and cleaning types are cited as available processes. Among them, an appropriate type is selected according to the size or type of fine particles to be collected and conditions for installation. For the efficiency of dust collection, a filtration system (by using bag filters and others) and electric systems are particularly outstanding and are therefore used widely in various areas of industry.
The theory of dust collection by an electrostatic precipitator is defined here as follows: fine particles are electrically charged by a corona discharge that is generated by a discharge electrode; and these electrically charged fine particles are drawn and collected by a dust-collecting counter electrode by using the Coulomb force. This electrostatic precipitator is characterized by notable advantages such as: 1) minimum pressure loss; 2) a large quantity gas processing capacity; and 3) a high rate of dust collection. Therefore, it is used in environments such as factories and power stations where a large quantity of contaminated air is released.
The electrostatic precipitator is commonly comprised of major structural components, i.e., a discharge electrode that is formed to have a large surface curvature, such as a needle or wire, to generate a corona discharge to charge fine particles; a collecting electrode, the counter electrode, which is formed into a plate to collect the charged particles; a rectifier to adjust the air flow in the electrostatic precipitator; a hammering device (dry type) and spray device (wet type) to separate the adhering fine particles from the dust-collecting electrode; a hopper that collects the separated particles; and attachments (an electrical power source for corona discharge and a charge control device).
The above-described hammering device is used in a dry-type electrostatic precipitator: it is used to hammer the dust-collecting electrode so that the fine particles that have been collected are shaken off and collected in the collecting means such as a hopper provided at the lower portion thereof. When a wet-type precipitator is used, the fine particles that have been collected in the dust-collecting electrode are washed off when a cleaning fluid such as water is sprayed. When a large quantity of fine particles have been collected on the particle-collecting electrode, the Coulomb force to attract the charged particles is compromised and the dust-collecting efficacy is reduced. Therefore to avert the condition in which dust is no longer collected in a steady state, the fine particles are removed from the collecting electrode by adopting a dry- and wet-type method, as described above.
More recently, on the other hand, a type in which the discharge and collecting electrodes are housed in an exchangeable cartridge is used. By using this embodiment, the cartridge is replaced after many particles have been collected on the collecting electrode (which compromises the dust-collecting efficacy), thus maintaining a steady dust-collecting efficacy. In many instances, used cartridges are subjected to a particle-removing operation in a special apparatus provided by the manufacturer so that they may be recycled. Thus, the apparatus is easily maintained, obviating the need to attach a dust-removing apparatus such as that described earlier, which contributes to down-sizing the entire apparatus and reducing production costs.
In view of the current condition described above, the applicant of the present invention invented an electrostatic precipitator that has a new structure and has filed a patent application (refer to Patent Documents 1 and 2).
[Patent Document 1]
    Unexamined Japanese Patent Publication No. 2003-126729[Patent Document 2]    Unexamined Japanese Patent Publication No. 2004-141826